Method and apparatus for generating terahertz wave

Abstract

A method and an apparatus for generating a terahertz wave, wherein one end face 12 a of a non-linear optical crystal 12 is positioned approximately orthogonally to a direction of generation of a terahertz wave 4 , pump light 2 and idler light 3 are totally reflected at an approximately same point 13 on the end face, and the generated terahertz wave 4 is emitted roughly vertically to the end face.

1. A method for generating a terahertz wave comprising: striking pump light into a non-linear optical crystal which generates the terahertz wave owing to a parametric effect; and generating idler light and the terahertz wave in a direction which satisfies a requirement for non-colinear phase matching,
 wherein one end face of the non-linear optical crystal is positioned approximately orthogonally to the direction of the generation of the terahertz wave, the pump light and the idler light are totally reflected at an approximately same point on the end face, and the generated terahertz wave is emitted roughly vertically to the end face. 
 
   
   
     2. The method for generating the terahertz wave according to  claim 1 , wherein incidence angles θp, θi of the pump light and the idler light on the end face of the non-linear optical crystal are larger than total reflection angles, respectively, and an incidence angle of the terahertz wave is smaller than a total reflection angle of the terahertz wave. 
   
   
     3. The method for generating the terahertz wave according to  claim 1 , wherein a climbing type resonator is constituted which strikes first laser light as the pump light and which totally reflects the idler light generated in the non-linear optical crystal at the total reflection point to amplify the idler light. 
   
   
     4. The method for generating the terahertz wave according to  claim 1 , wherein first laser light having a single frequency is used as the pump light, and another second laser light having a single frequency is optically injected in a direction of the generation of the idler light generated in the non-linear optical crystal. 
   
   
     5. The method for generating the terahertz wave according to  claim 1 , wherein a wavelength or an incidence angle of the pump light is changed to change a wavelength of the terahertz wave. 
   
   
     6. An apparatus for generating a terahertz wave comprising: a non-linear optical crystal which generates the terahertz wave owing to a parametric effect; and a laser unit which strikes pump light into the non-linear optical crystal, the apparatus being configured to generate idler light and the terahertz wave in a direction which satisfies a requirement for non-colinear phase matching,
 the apparatus being positioned so that one end face of the non-linear optical crystal is positioned approximately orthogonally to the direction of the generation of the terahertz wave, the pump light and the idler light are totally reflected at an approximately same point on the end face, and the generated terahertz wave is emitted close to perpendicular to the end face. 
 
   
   
     7. The apparatus for generating the terahertz wave according to  claim 6 , wherein incidence angles θp, θi of the pump light and the idler light on the end face of the non-linear optical crystal are larger than total reflection angles, respectively, and an incidence angle of the terahertz wave is smaller than a total reflection angle of the terahertz wave. 
   
   
     8. The apparatus for generating the terahertz wave according to  claim 6 , further comprising:
 a first laser unit which outputs first laser light as the pump light; and 
 a climbing type resonator which totally reflects the idler light generated in the non-linear optical crystal at the total reflection point to amplify the idler light. 
 
   
   
     9. The apparatus for generating the terahertz wave according to  claim 8 , wherein the first laser unit is a variable wavelength laser unit which can change a wavelength of the pump light. 
   
   
     10. The apparatus for generating the terahertz wave according to  claim 6 , further comprising:
 a first laser unit which outputs first laser light having a single frequency as the pump light; and 
 a second laser unit which optically injects another second laser light having a single frequency in a direction of the generation of the idler light generated in the non-linear optical crystal. 
 
   
   
     11. The apparatus for generating the terahertz wave according to  claim 10 , wherein the first laser unit is a variable wavelength laser unit which can change a wavelength of the pump light. 
   
   
     12. The apparatus for generating the terahertz wave according to  claim 6 , wherein a reflection reducing member which reduces reflectance of the terahertz wave is disposed at one end face of the non-linear optical crystal. 
   
   
     13. The apparatus for generating the terahertz wave according to  claim 6 , wherein a condenser lens which condenses the terahertz wave is disposed at one end face of the non-linear optical crystal.